On The Hunter, Mastodon have gone back to basics at the height of their powers. The Atlanta quartet’s fifth disc lacks two of its signature elements: a concept-album storyline and cover art by Paul Romano. But the band stand undiminished, combining Leviathan’s raging metal with the sterling production of the proggier Crack The Skye. Dueling anthemic riffs make album opener “Black Tongue” their heaviest track to date. (If it’s not, the late-in-the-album highlight “Spectrelight” is.) “The Octopus Has No Friends” somehow manages to be both ethereal and crushing. The guitar solo in “The Sparrow” is some transcendent shit. In the rager “Curl Of The Burl,” drummer/lyricist Brann Dailor lets loose percussive tsunamis to back tidal riffs. Execution matches ambition in the beautiful “The Creature Lives,” which adds a new dimension to the band’s classic-rock side, stacking a trippy keyboard intro, fantastic lyrics, clean singing and wall-of-sound vocal chorus. It sounds like an iffy proposition, but the band totally pull it off. It’s official: Mastodon are one of the all-time great hard-rock groups.